Numbers of rare eastern bettongs released into the predator-proof Mulligans Flat Woodlands Sanctuary in Canberra's north have exploded.
From the original 32 from Tasmania released in spring 2012, the bettongs more than doubled the following year. At the last count, in spring 2014, their numbers had reached 179. Latest estimates are more than 200.
An expansion of the sanctuary near Forde, which could involve adding three times the length of the $1.3-million, 12km-long enclosure, is being proposed to reintroduce more rare native species to the sanctuary.
Bettongs are rabbit-sized, kangaroo-like marsupials which aerate soil by digging for native truffles. They were common in this region until introduced foxes arrived, and have not been seen in their wild state on mainland Australia for more than 100 years.
An even smaller marsupial, the New Holland mouse, was released into Mulligans Flat sanctuary in 2013 after a long absence from the region. Monitoring in February found breeding mums and offspring scurrying about at night among the ground cover. The mouse and bettong are endangered and listed for protection in national biodiversity legislation.
Another reintroduced species, the bush stone-curlew, has recently been showing signs of breeding and more reintroductions at Mulligans Flat are planned.
Mulligans Flat sanctuary and the Jerrabomberra Wetlands Nature Reserve protect more than 600 hectares of the ACT's most significant landscapes. Alison Russell-French, chairwoman of a management trust for both areas, says the woodlands and wetlands showcase extraordinary environmental assets.
"We are very encouraged by the success of these initiatives The sanctuary is a space for rare plants and animals to recover and help rebuild a presence in the region. We have plans to expand and new programs to re-introduce new species into the broader area," Ms Russell French said.
"They are just plans, we are looking at different options and trying to seek support."
Scientists are studying two adjacent nature reserves, Mulligans Flat and Goorooyarroo Nature Reserves. The area totals 1146 hectares of yellow box - Blakey's red gum grassy woodland, the largest and most intact example of its type in the ACT.
While the sanctuary's 1.8m-high fence, which has an electric charge running through it, has kept out foxes and cats, eradicating rabbits has been more difficult. Rangers plan to step up efforts this year to eliminate every rabbit from the 480 hectare enclosure.
The presence of bettongs means rangers cannot use poison in the existing enclosure. Feral pests will be removed from the newly expanded areas before more native animals are reintroduced.